Thure larsson



Dec. 2 1924- T. LARSSON TUNNEL KILN Filed Jan. 22

Thure Larsson sw. www@ M q w Patented Dec. 2, 1924.

UNITED LS''I'ATES vPATENT OFFICE.

THURE LARSSON,.OI" WORCESTER, '.MASSAGHU'SETTS, ASSIGNOR'TO NORTON COMPANY,

V:0F.WORClilS'lER, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

TUNNEL KILN.

Application, filed January 2,2, 1924. Serial No. 687,679.

l To all rfui/i071@ ,may concern.'

Beit knoivnl that l, rliiUiir. LAnssoN, a-

citizen of the United States of `America,.,residing at 'lllorcesteig in the county oflllorcesy ter and, State -`of ll/lassachusetts, have invented certainwnew and useful linpi'ovements in rllunnel Kilns, of which the .following is a full, clear, andexact specification.

My invention `relates to tunnel kilns and more especially vto aniniprovement inthe construction of thoseof etheniutiie type in which the combustion of gasesdonot contact with the Ware. l

ln the muie typeof` tunnel kiln,v various constructions ,have .beeneniployed for. preheating the air Which isused inthe combustion zone and for cooling the Ware after it has been tired at the maximum temperature. This has been effected vby.conducting air from the outside of the kiln throughpipes disposed along the vside wal-lll of the; kiln chamber in' the cooling fone,I Where. .it accumulatesV heat from the Ware -which has been tired, and introducing itinto the combustion chamber. The aiisurrounding .the trucks of the. kilncars `which are` commonly used for conveying `the Ware through .such kilns, accumulates sonielof theheat which escapes ,from the car body, and this. airhas also been used in the combustion of the fuel. Such arrangements .dependl upon the con duction `ot heat. frein the Ware and kiln chamber through the Wallsfof theV air; tlue or conduit through which 'the4 air ,to be ,used for `combustion is .led to the` con'ibustion chaliibers. As a ,conseg'pienccu the cooling voperation vis not el'llcieiitvuiinl .consif'lerable heat which might,beusedjn the combustion Zoneis lost.. Furthermore,v such `constructions do not. provide inflexible `.method ofl tiring and cooling the ware at `adesired rate and accordingto an easily regulatable `teniperature curve.

It is accordingly an objectofiny .invenf tion ,to construct a tunnel kiln inwliich ,the Ware which hasbeen tired may be as rapidly cooledas its characteristics,and inode .of treatment Will permit,.and. to convey yas much of this heat as possible .to1 the air which is to be supplied to the combustion chamber or to other .portions ofthe kiln.

It is a furtherobject of thisinventionto provide means for controlling the,te1npverature condtionsfwithin the coolingand heat" ing rones of the kiln, whereby the heating .such rate as may be desired.

. and cooling curve of vthekiln, and consequently of the Ware being' iii-ed, may be more fully regulated than has heretofore been possible.

lVith these and other objects in view', as will be apparent from the `following disclosure, my invention resides in the combination of parts set forth in the specification and covered by the claims appendedhereto.

-ln the drawings .illustrating one embodiment of my invention:

Figure l is a longitudinal vertical section,

- partly broken away, of the kiln, on the lines 1 1 of Figs. 2, and 3;

Figure 2 is a transverse section on the line 2 2 of Fig. l; and

Figure 3 isa similar section on the `line 3 3 of Fig. l. lOn Figure l A B represent the preheating Zone, C l) t-he heating Zone and D .ll the cooling zone.

In accordance with my invention,` l. provide a tunnel kiln, Which has suitable means for lheating' the central Zone thereof, with regulatable openings from the external atmosphere into the coolingzone of the kiln chamber, andy preferably a plurality of such openings spaced apart, whereby airniay be introduced intol the cooling rone in desired volume to vary the` temperature conditions as may lbe required for Vthe park ticular Ware being treated.

I furthermore provide an air conduit adjacent the cooling @zoneof .the kiln for withdrawing air from the. kiln chamber. In yorder that;l the .tein- ]')eratnre curve `vv'ithin, thisvv portion o t the kiln may be `controlled. anuniber of suitablv spacedopenings from the kiln chambernto ingsare so located that air may ,be with l drawn Alroin lany portionof the cooling vzone and are regulated by valves controlled from the exterior of the kiln so that air may be withdrawn vthrough any orall of Vthem at In kilns of this typeit is customary to heat the `central portion bymeans of a combustion chamber or .inutile extending longitudinally ot the kiln, any suitable fuel such as oil or -gas ,being used for this purpose. In the present invention, I mayv pass the air, which is drawn from the cooling' Zone of the kiln.

into this chamber to support the combustion of the fuel or to vary the.tem1. erature conditions therein, and I may .introduce regulatahle amounts of this heated air` into valllll lltl rions portions of the combustion chamber, or by-pass any or all of it to an outlet.

In the specific embodiment of my invention illustrated by the accompanying drawings, I provide a tunnel kiln having foundation walls 1 upon which are built the outer vertical side walls 2 which are joined together by the roof 3 and held in place by the steel plates or girders 4. and cross rods 6. The foundation walls 1 are spaced apart leaving a floor space 7 along which are laid the tracks 8 upon which the kiln ears 9 are adapted to pass through the kiln. Along the inner edges of the foundation walls 1 are provided troughs 11 which form sand seals with thc flanges 12 on the sides of the kiln cars.

In order to provide an enclosed inutile. or kiln chamber 10 through which. the kiln ears and ware may travel, inner vertical walls 13 are built along the inner edges of the foundation walls 1, spa-ced apart from the outer side walls 2 and joined to the roof all 3 tlirougl'iout the length of the kiln. From the cooling zone of the kiln chamber, a number of longitudinally spaced openings Mare provided through the roof wall 3 to the exterior of the kiln for the passage of air, each having a slidable member 16 by which it may be regulated.

An air conduit 17 is formed on each side of the cooling zone of the kiln chamber by the lower portion of an inner vertical wall 13, the corresponding foundation and side walls 1 and 2 respectively, a kiln wall 18 at one end, a baille wall 19 at the opposite end and a horizontal partition 21. In each of the vertical side walls 13 and below the horizontal partitions 21 the openings 23 are provided, which connect the kiln chamber and said air conduit 17. Above each of the air conduits 17 is provided a similar and larger `air conduit 24 which is enclosed by the upper portions of an inner vertical wall 13 and of the corresponding` outer side wall 2, the roof wall 3, an end kiln wall. 18, a baflie wall 26 and partially enclosed at the bottom by a horizontal partition 21, leaving a space 30 between said baiie wall 1.9 and battle wall 26. Each of said horizontal partitions 21 between the air conduits 17 and 24: is provided with longitudinally spaced openings 27 which may be regulated from the exterior of the kiln by slidable members 28 inserted through the openings 29 in the outer walls 2.

In the central and heating zone of the kiln CD, the longitudinal combustion chambers 31 are each formed by an inner vertical wall 11,3, an outer vertical side wall 2. the roof wall 3, a horizontal partition 32. a refractory bafflewall 26 and one of the end kiln walls 18. The wall 13 in the heating zone is made of a suitable refractory material capable of withstanding high temperatures, and in order that it may be laterally supported to prevent deformation when heated, I may form it of two L-shaped members which are arranged with the horizontal flanges 33 in contact and supported on the transverse partition 32. rlhese flanges are shown as built into and tied with the inner refractory brick wall 34 which lines the vertical side walls 2 of the kiln and is spaced therefrom by suitable insulating material. .In order to provide for a uniform distribution of heat in the muffie, the flanges are formed with numerous perforations, as shown.

Parallel to each con'ibustion cl'ianrber and beneath it is an air conduit 35 formed by the foundation wall 1, the lower portion of the inner vertical side wall. 34, a vertical wall 36 adjacent the refractory car body, one of ythe end kiln walls 18, the baffle wall 19 and the horizontal partition 32, this conduit opening into the cooling conduit 24 through opening 3() between said haiiie wall 19 and the baffle wall 26. In each of said horizontal partitions 32 are longitudinally spaced openings 37 connecting the air conduits 35 with the combustion chambers 31, which may be regulated from the exterior of the kiln by the slidable members 38 inserrted into slots 39 through the outer side walls. Burners 41 are inserted into each of the combustion chambers through openings 42 in the side walls 2 and 34 for'the introduction of fuel. Outlets 43 are' provided in the kiln walls at the ends of the `combustionchambers adjacent the ware entrance. These outlets lead through fines 44 to the fan 45. It is to be noted that the end openings 4G in the conduit 35 communicate directly with fines 44 and so serve for by-passing a desired portion of the heated air around the mutiies so that all of the air used in the cooling zone need not be fed into the muflie.

The particular tunnel kiln` which I have thus described and illustrated in the accon'ipanying drawings, is representative of one of the inutile type in which my invention has been eml'iodied. rlhe method of operating it is in general similar to that for other tunnel kilns. in that the ware to be fired is loaded upon cars, which are run into the kiln chamber until it is filled from end to end. The cars are then su 1- cessively withdrawn from the exit end and cars loaded with unred ware are introduced at the entrance end of the chamber, by any well known means adapted for the purpose. The central or hot zone of the kiln is maintained at approximately the temj'ierature to which the ware is to be treated, by operatiiig the burners in the combustion chambers accordingly. Upon passing through the kiln. the Ware is heated slowly to the maximum temperature at which it is usually held for some time, called the soaking period. and then cooled gradually to such temperature as will permit its removal from the kiln, It. is customary to makethe'rate of travel through the kiln constant. determining the heating, soaking and cooling' periods by the lengths of the corresponding heating-up. central and cooling zones ot the kilnchamber respectively.

I have therefore provided for controlling the temperatures in the'cooling zone of the kiln chamber by drawing regulatable amounts of air at atmospheric temperature from the exterior ot the kiln into the kiln chamberfand in direct contact with the ware at such points as may be desirable. thus cooling the Ware at any desired rate, absorbing the heattrom it directly by the air thus introduced as well as through the walls of the conduits through which such air is Withdrawn fromv the kiln chamber. The flow of air which has beenthus heatedmay be controlled as by the regulatableopenings between the kiln chamber and theair conduit and may be used in the combustion chambers for ignition of the fuel or withdrawn directly from the kiln; In order that the air which isto bepassed into'the combustion chamber may not lower the temperature of combustion or prove insutiieient to support it, means are provided for controlling the volume of such air to be'introduced and its rate ot' flow by spaced regulatable openings, such as have been described. The heated air which is tobe withdrawn from the kiln Without passing through the combustion chamber may be drawn through air conduits located adjacent the heating-up zone or througlr the end of the combustion chamber opposite thelocation of the burners, and drawn oit with the products of combustion, serving in either case to transmit heat to the incoming ware.

The Ware, which has been held at the temperature ot the hot zone for the desired length ot time, may be cooled as rapidly as is consistent with its resistance to .such temperature or heat changes or .as slowly as would naturally result. trom the radiation o't heat through the kiln walls, or at anyl desired rate between these limits. `Moreover, the temperature curve prescribed by the heat treatment employed may be closely followed by thus controlling the rate of cooling of the ware at the various portions of the cooling zone through which it passes. The heat is effectively removed from the ware in the cooling zone by the air coming into direct contact with it and is thus directly transferred to the combustion chamber or to such other parts of the kiln as may be desired.

Further advantages which are to be obtained by the application of my invention are that such Ware may be cooled either from the maximum kiln temperature to the temperature ot the atmosphere or through any iutern'iediate rangeI ot temperatures. and at the same time he under the control of the operator throughout the cooling period. As a consequence ot these advantages, a kiln having a shorter cooling zone than would otherwise be necessary may be einployed and thelength ot' time required tor any particular article to be passed through the kiln appreciably shortened.

It will be apparent from my disclosure that various moditicationsfmay be made ot my invention by changes in the design or yoperation of any particular construction. but it .is to beunderstood that such modifications or applications are considered as embodied in the following claims.

Having thus described my invention7 whatl I claim as new and desire to secure by Letters Patent is:

l. A tunnel kiln comprising a touiidation and side'andtop walls forming a kiln chamber for the passage of ware, means tor heating the central zone of the kiln, means providing regulatable air openings from the external atmosphere into the interior oti the kiln lchamber which are spaced longitudinally of the cooling zone for varying: the temperature curve thereof, and means for drawing air` through said` openings into the kiln chamber.

2. A tunnel kiln comprising walls spaced to form a kiln chamber for thepassage ot Ware, said kiln having an air conduit disposed adjacent the cooling zone, means providing a plurality of spaced regulatable openings from different portions ot the cooling zone ot the kiln into the conduit for varying the temperature curve of the cooling zone and means tor drawingair through said conduit.

3. A tunnel kiln comprising a foundation and side and top wallsl spaced apart to 'torm a kiln chamber for the passage ot ware.y au air conduit in the cooling zone ot the kiln. a combustion inutile disposed longitiuliually oty the heating Zone ot the kiln. means providing a. series ot' spaced inlet passages 'trom the cooling zone oi the kiln chamber to the air conduit, means for iiidependently regulating the-inflow ot air through said pas-- sages, and means for drawing air from the cooling Zone into said air conduit and from the kiln.

4. A tunnel kiln comprising a foundation and side and top walls spaced apart to 'form a. kiln chamber for the passage ot ware. an air conduit adjacent the cooling zone ot the kiln, a combustion Inutile disposed longitudinally of the heating Zone of the kiln. means providing a series of space-d regulatable inlets into said air conduit from widely sepa-- rated portions of the cooling Zone of the kiln chamber` means providing a regulatable opening from said air conduit into said combustion muile, and means for drawing air from the cooling zone of the kiln chamber through said air conduit, into and through said combustion Inutile and from thel kiln.

A tunnel kiln comprising walls arranged to form a kiln chamber for the passage of ware, an air conduit disposed adjacent the cooling zone of the kiln and having an air inlet from said zone, a combustion Inutile disposed longitudinally of the heating zone of the kiln, means providing a series of regulatable inlets from the air conduit into longitudinally spaced portions of the combustion chamber, and means for drawing air through the conduit and the combustion chamber.

6. A tunnel kiln comprising walls forming a kiln chamber for the passage oi? ware, a combustion chamber in the central zone of the kiln, an air conduit in the cooling Zone of the kiln, said kiln chamber having spaced air inlets from the exterior atmosphere into the cooling zone and a series of regulatable spaced openings into said conduit Ytrom the cooling zone, said conduit opening into the combustion chamber, and means for drawing air from the exterior of the kiln into the kiln chamber, thence into the air conduit and through the combustion chamber.

7. A tunnel kiln comprising a foundation and side and top walls to orm a kiln chamber for the passage of ware, an air conduit in the cooling zone, a combustion muflie in the heating Zone, a series of spaced regulatable inlets from the cooling Zone of said kiln chamber into the air conduit, a communication between the air conduit and the combustion muitle, and means for drawing air from the kiln chamber, through the airv conduit and through the combustion mufile.

8. A tunnel kiln comprising walls forming a kiln chamber for the passage of ware, a combustion chamber in the central zone of the kiln, an air conduit in the cooling zone of the kiln, said kiln chamber having spaced air entrances from the exterior atn'lospliere to different portions of the cooling zone and an opening into said air conduit, means` providing longitudinally spaced regulatable openings from said air con duit :into said combustion chamber, and means for drawing air into the kiln chamber through said entrances, thence through the air conduit and through the combustion chamber.

9. A tunnel kiln comprising walls forming a kiln chamber having an air entrance to the cooling zone, an air conduit adjacent to and having an opening leading from the cooling zone of the kiln chamber, a con'ibus-'f tion chamber in the heating zone of the kiln having an opening from said air conduit, means for drawing air into the cooling zone of the kiln through said air entrance into said conduit and thence in predetermined amounts through said combustion cllamber to an exit, and means for by-passing a portion of such air around the combustion chamber to the air exit.

10. A tunnel kiln comprising a Jfoundation and side and top walls spaced apart to form a kiln chamber for the passage ot.' Ware, an air conduit adjacent the cooling zone of the kiln chamber, means providing a series of regulatable openings from the cooling zone of the kiln chamber to the air conduit for varying the temperature curve within the kiln, a combustion chamber disposed longitudinally of the heating zone ot the kiln chamber, an air conduit adjacent thereto having a series of spaced regulatable "1" openings into the combustion chamber, means for supplying combustible fuel. to the latter chamber, and means for drawing air from the cooling zone of the kiln through said air conduits and into the combustion chamber and for by-passing any or all or' such air around the combustion chamber.

1l. A tunnel kiln comprising a `foundation and outer side and top walls forming a kiln chamber for the passage of Ware, means including inner refractory walls spaced from the outer side walls forming a combustion chamber on each side of the central zone ot' the kiln, further inner walls cooperating with the outer Walls in the cooling Zone forming a longitudinal air conduit, means providing a series o't' regulatable openings from the exterior atmosphere into the cooling Zone ot' the kiln chamber, said air conduit having an air entrance Jfrom the kiln chamber and an exit to said combustion chamber, and means for drawing air vfrom the exterior atmosphere into the kiln chamber and thence through the air rond uit and through the combustion chamlier.

Signed at Worcester, lWassachusetts, this 14th day of Jan., 1924:.

THURE LARSSON.

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